Building Materials and Products www.dvfu.ru/en/vestnikis
DOI: http://www.dx.doi.org/10.24866/2227-6858/2020-1-13
Shmit'ko E., Makushina Yu., Bel'kova N., Milokhin I.
EVGENY SHMITKO, Doctor of Engineering Sciences, Professor, AuthorID: 175619,
SPIN: 3669-7239, e-mail: verlnata@mail.ru
JULIA MAKUSHINA, Postgraduate, e-mail: makuschina2000@gmail.com
NATALIA BELKOVA, Associate Professor, SPIN: 6502-2935,
ORCID: 0000-0002-3005-5956, e-mail: verlnata@mail.ru
ILYA MILOKHIN, MS Student, e-mail: i.miloxin@yandex.ru
Department of Construction Materials, Products and Structures Technology
Voronezh State Technical University
84, 20th Anniversary of October, Voronezh, Russia, 394006
Moist shrinkage of concrete:
influence of composition and structure
of the applied plasticizing additives
Abstract: Moisture shrinkage of concrete has a negative impact on the durability of concrete and reinforced concrete structures and is therefore among the rated design characteristics of concrete used for these structures. The humidity shrinkage values contained in the building codes are used for clean, non-compounding concrete. However, concrete mixtures with structure-modifying additives were studied and applied in construction practice throughout the recent 2–3 decades. Such additives, along with mineral components typically include super- and hyper-plasticizers as they significantly increase the moisture shrinkage ratio (compared to non-thickening concretes). At the same time, the positive effect of plasticizer may conflict with the increasing ratio of humidity shrinkage, which in turn depends on the chemical composition and structure of the plasticizer additive. This article presents the results of experimental studies using two groups of plasticizers: the first based on lignosulfonates (Reoplast NSL) and polycarboxylate esters, the second based on naphthalene sulfonates (PMF – NLC) and melamine sulfonates. It was defined that the plasticizers of the selected groups have different effects on the surface tension at the liquid – gas interface and subsequently on the magnitude of capillary compressive pressure and shrinkage; this effect is significant and depends on composition and structure of the superplasticizer. Conclusion is that it is necessary to take this influence into account when adjusting the existing and developing new “Recommendations for consideration of creep and shrinkage of concrete”, international and state standards, and standards of particular organizations.
Keywords: moisture shrinkage, plasticizer additive, cement stone, water-cement ratio, plasticizer additive structure, chemical composition, normative parameters.
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